package com.android.support.jhf.utils;

import java.io.UnsupportedEncodingException;
import java.util.UUID;

import android.telephony.TelephonyManager;
import android.content.Context;
import android.content.SharedPreferences;
import android.provider.Settings.Secure;

/**
 * 获取设备唯一号
 * 
 * @author hongfeijia
 * 
 */
public class UniqueDeviceIdentifiers {

	protected static final String PREFS_FILE = "device_id.xml";
	protected static final String PREFS_DEVICE_ID = "device_id";

	protected static UUID sUuid;
	
	private static final String ENCODING = "UTF-8";

	public UniqueDeviceIdentifiers(Context context) {

		if (sUuid == null) {
			newUuid(context);
		}

	}

	private synchronized void newUuid(Context context) {
		if (sUuid == null) {
			final SharedPreferences prefs = context.getSharedPreferences(
					PREFS_FILE, 0);
			final String id = prefs.getString(PREFS_DEVICE_ID, null);

			if (id != null) {
				// Use the ids previously computed and stored in the prefs file
				sUuid = UUID.fromString(id);

			} else {

				final String androidId = Secure.getString(
						context.getContentResolver(), Secure.ANDROID_ID);

				// Use the Android ID unless it's broken, in which case fallback
				// on deviceId,
				// unless it's not available, then fallback on a random number
				// which we store
				// to a prefs file
				try {
					if (!"9774d56d682e549c".equals(androidId)) {
						sUuid = UUID.nameUUIDFromBytes(androidId
								.getBytes(ENCODING));
					} else {
						final String deviceId = ((TelephonyManager) context
								.getSystemService(Context.TELEPHONY_SERVICE))
								.getDeviceId();
						sUuid = deviceId != null ? UUID
								.nameUUIDFromBytes(deviceId.getBytes(ENCODING))
								: UUID.randomUUID();
					}
				} catch (UnsupportedEncodingException e) {
					throw new RuntimeException(e);
				}

				// Write the value out to the prefs file
				prefs.edit().putString(PREFS_DEVICE_ID, sUuid.toString())
						.commit();

			}

		}
	}

	/**
	 * Returns a unique UUID for the current android device. As with all UUIDs,
	 * this unique ID is "very highly likely" to be unique across all Android
	 * devices. Much more so than ANDROID_ID is.
	 * 
	 * The UUID is generated by using ANDROID_ID as the base key if appropriate,
	 * falling back on TelephonyManager.getDeviceID() if ANDROID_ID is known to
	 * be incorrect, and finally falling back on a random UUID that's persisted
	 * to SharedPreferences if getDeviceID() does not return a usable value.
	 * 
	 * In some rare circumstances, this ID may change. In particular, if the
	 * device is factory reset a new device ID may be generated. In addition, if
	 * a user upgrades their phone from certain buggy implementations of Android
	 * 2.2 to a newer, non-buggy version of Android, the device ID may change.
	 * Or, if a user uninstalls your app on a device that has neither a proper
	 * Android ID nor a Device ID, this ID may change on reinstallation.
	 * 
	 * Note that if the code falls back on using TelephonyManager.getDeviceId(),
	 * the resulting ID will NOT change after a factory reset. Something to be
	 * aware of.
	 * 
	 * Works around a bug in Android 2.2 for many devices when using ANDROID_ID
	 * directly.
	 * 
	 * @see http://code.google.com/p/android/issues/detail?id=10603
	 * 
	 * @return a UUID that may be used to uniquely identify your device for most
	 *         purposes.
	 */
	public String getDeviceUuid() {
		return sUuid.toString();
	}
}
